A technique in which an operation system (OS) operating on a computer adjusts memory allocation to improve memory usage efficiency has been known. For example, in a deduplication technique disclosed in NPL 1, the OS selects two unit areas from memory areas recognized by the OS, and compares data pieces of the two selected unit areas with each other. When the two unit areas store the same data, the OS determines that the two unit areas are duplicated, and merges the two unit areas. Thus, more efficient memory usage is achieved.